Probing the Dirac or Majorana nature of the Heavy Neutrinos in pure leptonic decays at the LHC

Abstract

We propose a strategy for distinguishing the Dirac / Majorana character of heavy neutrinos with masses below the $W$ boson mass, using purely leptonic decays at the LHC. The strategy makes use of a forward-backward asymmetry of the opposite charge lepton in the $W^{+}\to l^{+}{l}^{+}{l}^{{}^{\prime }-}\nu$ decay. In order to check the experimental feasibility of the model, we show, through a numerical analysis, that in the decay $W^{+}\to e^{+}{e}^{+}{\mu }^{-}\nu$ the two positrons in the final state can be distinguished for different ranges of the heavy neutrino masses. Finally, we estimated the number of events of $W^{+}\to e^{+}{e}^{+}{\mu }^{-}\nu$ for a Dirac and Majorana $N$ neutrino. For an integrated luminosity of 120 fb${}^{-1}$ at LHC RUN II, signals can be found if heavy-to-light neutrino mixings are $|U_{N\mu }{|}^2,|U_{Ne}{|}^2\gtrsim 10^{-6}$.

Comments: 7 pages, 4 figures, references added